JP2013086771A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for suppressing occurrence of conicity while improving steering stability and flat spot resistance.SOLUTION: Both ends of a carcass layer 6 are folded from the inner side to the outer side around a bead core 4 and a bead filler 5, a flipper layer 7 composed of organic fiber cords is interposed between the bead core 4 and the bead filler 5 on the inner peripheral side, a belt layer 8 and a belt cover layer 9 are arranged on the outer peripheral side of the carcass layer 6 of a tread part 1, and a mounting direction to a vehicle is specified. The height of the bead filler 5 is reduced more on the outer side (Bo) when mounted on the vehicle than the inner side (Bi) when mounted on the vehicle, the height of the flipper layer 7 is increased more on the outer side (Fo) when mounted on the vehicle than the inner side (Fi) when mounted on the vehicle, the maximum height is turned to ≤0.7 times of a tire cross section height SH, and the number of ends of reinforcing cords constituting the belt cover layer 9 is made smaller on the outer side when mounted on the vehicle than on the inner side when mounted on the vehicle.

Description

  The present invention relates to a pneumatic tire that suppresses the occurrence of conicity while improving steering stability and flat spot resistance.

  High-performance pneumatic tires for Europe require a high level of handling stability and flat spot resistance. Here, the flat spot phenomenon means that a tire that has become hot due to traveling stops and is cooled while being loaded, and the roundness of the tire collapses and deforms mainly in the ground contact area. When the vehicle travels again in this state, it means that vibration is generated every time the tire rotates once. In order to suppress the flat spot phenomenon, it is necessary to reduce the residual deformation at the time of flat spot formation and to speed up the recovery of the residual deformation. For example, the height of the bead filler is reduced or the side portion is configured. For example, the number of reinforcing members is reduced. On the other hand, in order to improve steering stability, it is possible to increase the height of the bead filler in order to ensure side rigidity and improve cornering characteristics, or to configure the side part with a reinforcing member such as a cord reinforcing layer. Done. Therefore, steering stability and flat spot resistance are contradictory, and it has been difficult to improve both.

  In order to improve steering stability, Patent Document 1 discloses that the height of the bead filler disposed on the outer side when the vehicle is mounted is larger than the height of the bead filler on the inner side when the vehicle is mounted, and a wire insert layer is provided only on the outer side when the vehicle is mounted. Proposed asymmetric pneumatic tires to be arranged. However, in this asymmetric pneumatic tire, there is a concern that the flat spot resistance deteriorates. Furthermore, in the pneumatic tire having an asymmetric structure, the conicity component is deteriorated, and there is a problem that the vehicle flow is likely to occur when traveling straight ahead. Therefore, a pneumatic tire that has improved both steering stability and flat spot resistance and suppresses the occurrence of conicity has not yet been obtained.

JP-A-61-253205

  An object of the present invention is to provide a pneumatic tire in which the occurrence of conicity is suppressed while improving steering stability and flat spot resistance.

  The pneumatic tire of the present invention that achieves the above object includes a bead core and a bead filler in which at least one carcass layer is mounted between a pair of right and left bead portions, and both ends of the carcass layer are embedded in the bead portions. The carcass layer is folded back from the inside of the tire so as to be wrapped, and a flipper layer made of organic fiber cord is interposed on the inner peripheral side of the folded carcass layer so as to wrap the bead core and the bead filler. In a pneumatic tire having a configuration in which a belt layer and a belt cover layer are disposed on the outer peripheral side of the tire and the mounting direction with respect to the vehicle is specified, the height of the bead filler on the outer side when the vehicle is mounted is set to the inner side when the vehicle is mounted. The height of the flipper layer outside the bead filler is less than the height of the bead filler and is mounted on the vehicle. It is larger than the height of the flipper layer on the inner side when worn, and the maximum height is 0.7 times or less of the tire cross section height, and the number of ends of the reinforcing cord constituting the belt cover layer is set on the outer side when the vehicle is mounted. The number of ends is smaller than the number of inner ends when the vehicle is mounted.

  In the pneumatic tire of the present invention, when the rim is assembled, the bead filler height on the outer side is smaller than the inner side when the vehicle is mounted, and the height of the flipper layer is mounted on the vehicle. Since the outer side is larger than the inner side when the vehicle is mounted, the side rigidity of the entire rim-assembled pneumatic tire is increased, and steering stability can be improved. Further, by reducing the height of the bead filler on the outside when the vehicle is mounted, the flat spot resistance can be made equal to or higher than the conventional level. In addition, the number of ends of the reinforcing cords that make up the belt cover layer is less on the outside when the vehicle is installed than on the inside when the vehicle is installed, thereby reducing residual deformation during flat spot formation and improving flat spot resistance. Since the weight on the outer side of the tire tread portion when mounted on the vehicle is made smaller than the weight on the inner side when mounted on the vehicle, deterioration of the conicity component due to the asymmetric structure of the bead portion can be suppressed.

  The difference between the height of the bead filler on the outer side when the vehicle is mounted and the height of the bead filler on the inner side when the vehicle is mounted is in the range of 10 to 50% of the height of the cross section of the tire. The difference in height of the inner flipper layer is in the range of 20 to 40% of the tire cross-section height, and the number of ends of the reinforcing cord of the outer belt cover layer when the vehicle is installed is greater than the number of inner ends when the vehicle is installed. It is preferable to reduce by 10 to 30%.

  The reinforcing cord constituting the belt cover layer is preferably a composite fiber cord composed of at least two kinds of organic fibers.

  The organic fiber cord constituting the flipper layer is preferably made of non-thermoplastic organic fibers.

Wherein it preferably has a storage modulus at 100 ° C. of the bead filler (E _'100) and the storage modulus at 20 ° C. (E' ratio _{20) (E '100 / E} ' 20) is 0.5 or more.

  The folded height of the carcass layer is preferably in the range of 0.2 to 0.4 times the tire cross-sectional height.

It is sectional drawing of the tire meridian direction which shows an example of embodiment of the pneumatic tire of this invention.

  FIG. 1 is a meridian direction sectional view showing an example of an embodiment of a pneumatic tire of the present invention.

  In FIG. 1, the mounting direction of a pneumatic tire is specified with respect to the vehicle. Reference numeral IN represents an inner side when the vehicle is mounted, and reference numeral OUT represents an outer side when the vehicle is mounted. This pneumatic tire includes a tread portion 1, a sidewall portion 2, and a bead portion 3. A carcass layer 6 is mounted between a pair of left and right bead cores 4 embedded in the bead portion 3, and both end portions thereof are bead cores 4 respectively. In addition, the tire is folded from the inside to the outside around the bead filler 5. A flipper layer 7 made of an organic fiber cord is interposed on the inner periphery side of the folded carcass layer 6 so as to wrap the bead core 4 and the bead filler 5. Further, a belt layer 8 composed of two plies is disposed over the circumference of the tire on the outer peripheral side of the carcass layer 5 of the tread portion 1, and a belt cover layer 9 is further disposed on the outer side thereof. In the illustrated example, the belt cover layer 9 includes a belt full cover layer and a belt edge cover layer. However, the belt cover layer 9 is not limited to this example. One or two belt full cover layers, one layer Alternatively, two belt edge cover layers and any combination thereof can be configured.

  In the pneumatic tire of the present invention, the bead filler 5, the flipper layer 7, and the belt cover layer 9 have an asymmetric structure on the inner side when the vehicle is mounted and the outer side when the vehicle is mounted. That is, the height Bo of the bead filler 5 on the outer side when the vehicle is mounted is made smaller than the height Bi of the bead filler 5 on the inner side when the vehicle is mounted, and the height Fo of the outer flipper layer 7 is set on the inner side when the vehicle is mounted. The height Fi of the flipper layer 7 is set to be greater than 0.7 times the tire cross-section height SH, and the number of ends of the reinforcing cords constituting the belt cover layer 9 is set to the outside when the vehicle is mounted. The number of ends is made smaller than the number of inner ends when the vehicle is mounted. When a pneumatic tire assembled on a wheel is mounted on a vehicle, the vehicle side from the tire equator is the inside when the vehicle is mounted, and the opposite side is the outside when the vehicle is mounted.

  A wheel for assembling a pneumatic tire with a rim generally has a disk or spoke on the outside when the vehicle is mounted. For this reason, as for the side rigidity of the pneumatic tire assembled on the wheel, the outer rigidity when the vehicle is mounted is likely to be larger than the inner side rigidity when the vehicle is mounted. At this time, if the height Bo of the bead filler 5 disposed on the outside when the vehicle is mounted is increased, the tire rigidity is increased and the steering stability is improved. However, with respect to the flat spot resistance, the side rigidity on the outside is excessively large when the vehicle is mounted, and this causes a large residual deformation when the flat spot is formed, so that the flat spot resistance is deteriorated.

  For this reason, in the present invention, the height Bo of the bead filler 5 disposed on the outer side when the vehicle is mounted is smaller than the height Bi of the bead filler 5 disposed on the inner side when the vehicle is mounted. It is possible to improve the steering stability by increasing the side rigidity and to suppress the deterioration of the flat spot resistance. Here, the height Bi, Bo of the bead filler 5 is a radial distance from the tire radial direction inner end of the bead portion to the tire radial outer end of the bead filler 5.

  In the present invention, the difference (Bi-Bo) between the height Bo of the bead filler 5 disposed on the outer side when the vehicle is mounted and the height Bi of the bead filler 5 disposed on the inner side when the vehicle is mounted is preferably the tire cross-section height SH. Is preferably 10 to 50%. If the difference in height (Bi-Bo) between the left and right bead fillers is less than 10% of the tire cross-section height SH, the rigidity of the side portion cannot be sufficiently increased. Further, if the difference (Bi-Bo) exceeds 50% of the tire cross-section height SH, the conicity component may be extremely deteriorated. Here, the tire cross-section height SH is a radial distance from the tire radial inner end of the bead portion to the tire radial outer end of the tread portion 1.

In the pneumatic tire of the present invention, the ratio (E ′ ₁₀₀ / E ′ ₂₀ ) of the storage elastic modulus (E ′ ₁₀₀ ) at ₁₀₀ ° C. and the storage elastic modulus (E ′ ₂₀ ) at 20 ° C. of the bead filler 5 is preferably 0. .5 or more, more preferably 0.7 to 1.0. By setting the storage elastic modulus ratio (E ′ ₁₀₀ / E ′ ₂₀ ) to be 0.5 or more, it is possible to reduce the change in elastic modulus at the time of flat spot formation and to reduce the flat spot formation level. Moreover, since heat drooping property can be suppressed, steering stability during high speed traveling can be improved. The storage elastic modulus (E ′ ₂₀ and E ′ ₁₀₀ ) at 20 ° C. and 100 ° C. is measured under the conditions of a frequency of 20 Hz, an initial strain of 10%, and a dynamic strain of ± 2%. The ratio of the storage modulus of the bead filler (E ′ ₁₀₀ / E ′ ₂₀ ) is preferably adjusted appropriately by blending the rubber composition constituting the bead filler. For example, in the case of an NR / BR blended rubber composition For example, increasing the blending amount of BR or increasing / decreasing the blending amount of the resin component or the plasticizer.

  In the present invention, a flipper layer 7 made of an organic fiber cord is disposed so as to wrap the bead core 4 and the bead filler 5, and the carcass layer 6 is folded back from the inner side in the tire axial direction so as to wrap the flipper layer 7. The maximum height of the flipper layer 7 is 0.7 times or less, preferably 0.4 to 0.7 times the tire cross-section height SH. When the height of the flipper layer 7 exceeds 0.7 times the tire cross-section height SH, the tire rigidity becomes excessively high and the flat spot property is hindered.

  Further, by making the height Fo of the flipper layer 7 disposed outside when the vehicle is mounted larger than the height Fi of the flipper layer 7 disposed inside when the vehicle is mounted, the height Bo of the bead filler 5 on the outside when the vehicle is mounted. When is reduced, side rigidity can be compensated for and steering stability can be improved. Here, the heights Fi and Fo of the flipper layer 7 are radial distances from the tire radial inner end of the bead portion to the tire radial outer end of the flipper layer 7.

  In the present invention, the difference (Fo-Fi) between the height Fo of the flipper layer 7 disposed on the outer side when the vehicle is mounted and the height Fi of the flipper layer 7 disposed on the inner side when the vehicle is mounted is preferably the tire cross-section height SH. Is preferably 20 to 40%. If the difference in height difference (Fo-Fi) between the left and right flipper layers with respect to the tire cross-section height SH is outside the above range, when the height of the left and right bead fillers is asymmetrical, The effect of supplementing rigidity cannot be obtained sufficiently.

  The organic fiber cord constituting the flipper layer is preferably a highly elastic organic fiber cord, and more preferably an organic fiber cord made of a non-thermoplastic resin. Examples of such an organic fiber cord include an aramid fiber cord and a PBO (polyparaphenylene benzobisoxazole) fiber cord. Moreover, high elasticity means that the elasticity modulus of the organic fiber cord measured between the tensile loads of 10N to 99N is preferably 4.5 to 18.0 GMa. By forming the flipper layer with such a highly elastic organic fiber cord, it is possible to suppress the deformation from remaining when the flat spot is formed.

  In the pneumatic tire of the present invention, the number of ends of the reinforcing cords constituting the belt cover layer 9 is set so that the number of ends on the outside when the vehicle is mounted is smaller than the number of ends on the inside when the vehicle is mounted. This reduces residual stress on the outside when the vehicle is mounted during flat spot formation, improves flat spot resistance, and reduces the weight on the outside of the tire tread when mounted on the vehicle to less than the weight on the inside when the vehicle is mounted. Therefore, it is possible to suppress deterioration of the conicity component due to the asymmetric structure of the bead portion. This is because the conicity component has a large mass sensitivity, and by reducing the number of ends of the reinforcing cord, the weight of the tread can be reduced and the conicity component can be suppressed. The vehicle flow can be improved. Here, the number of reinforcement cord ends means the number of reinforcement cords driven per 50 mm of the belt cover layer.

  In the present invention, the number of ends of the reinforcing cords on the outer belt cover layer when the vehicle is mounted is preferably 10 to 30% less than the number of ends on the inner side when the vehicle is mounted. When the number of ends on the outside of the vehicle is outside the above range, the effect of improving conicity and flat spots is small.

  As the reinforcing cord constituting the belt cover layer, an organic fiber cord can be used, and a composite fiber cord composed of at least two kinds of organic fibers is preferable. Examples of the organic fiber cord include low elastic fiber such as nylon 6 fiber and nylon 66 fiber, and high elastic fiber such as aramid fiber, polyethylene naphthalate fiber, and polyolefin ketone fiber. The composite fiber cord is preferably a combination of at least one low-modulus fiber and at least one high-modulus fiber, and is preferably a nylon 6 (66) -aramid composite fiber cord. By forming the belt cover layer with such a composite fiber cord, residual deformation at the time of flat spot formation can be reduced, and flat spot resistance can be improved.

  In the pneumatic tire of the present invention, the folded height of the carcass layer 6 is preferably in the range of 0.2 to 0.4 times the tire cross-section height SH. If the turn-up height of the carcass layer 6 is less than 0.2 times or more than 0.4 times the tire cross-section height SH, it becomes difficult to achieve both steering stability and flat spot performance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

In the pneumatic tire of tire size 225 / 55R17, ten types of pneumatic tires (Examples 1 to 4, Comparative Example 1) having different configurations of the bead filler, the flipper layer, and the belt cover layer as shown in Tables 1 and 2 are used. ~ 6) were produced. In Tables 1 and 2, the inner bead filler height Bi when the vehicle is mounted, the outer bead filler height Bo when the vehicle is mounted, the inner flipper layer height Fi when the vehicle is mounted, and the outer flipper layer height Fo when the vehicle is mounted. The height TUH of the folded end portion of the carcass layer is expressed as a ratio to the vehicle cross-sectional height SH, that is, Bi / SH, Bo / SH, Fi / SH, Fo / SH, and TUH / SH. Frequency 20 Hz, initial strain 10%, dynamic strain of ± 2% relative condition storage modulus at 100 ° C. in the measured bead filler in the (E _'100) and the storage modulus at _{20 ℃ (E' 20) (} E '100 / E ′ ₂₀ ) is shown in the table. As the organic fiber cord constituting the flipper layer, “aramid” (aramid fiber cord; 1100T / 2) or “nylon” (nylon fiber cord; 940T / 2) is used, and the number of ends of each organic fiber cord is mounted on the vehicle. At the time of inside and outside, 30/50 mm was common. As the organic fiber cord constituting the belt cover layer, “nylon” (nylon fiber cord; 940T / 2) or “nylon / aramid” (nylon / aramid composite fiber cord; aramid 1670T / 2 + nylon 1400T / 1) was used. .

  About the obtained 10 types of pneumatic tires, flat spot resistance, steering stability, and conicity were evaluated by the following methods.

Flat spot resistance After mounting the obtained pneumatic tire on a wheel with a rim size of 17 x 7 JJ, mounting it on a 2.5L sedan foreign test vehicle, and preliminarily running 105km (24 minutes) under the condition of air pressure 230kPa Then, the vehicle was stopped and allowed to stand for 1 hour to be in a flat spot forming condition. Thereafter, RFV when the test run was measured again was measured. The evaluation results were expressed as an index with Comparative Example 1 taken as 100, and are shown in the column of “Flat spot resistance”. It means that flat spot resistance is excellent, so that the value of this index | exponent is large.

Steering stability The obtained pneumatic tire is assembled on a wheel with a rim size of 17 x 7 JJ, mounted on a 2.5L sedan test vehicle, and a 3km round test course is performed at 180km / h under conditions of air pressure of 230kPa. The steering stability when running was evaluated sensitively by three expert panelists. The evaluation results were expressed as an index with Comparative Example 1 set to 100, and are shown in the column “Steering stability”. The larger the value of this index, the better the steering stability.

Conicity When the obtained pneumatic tire is mounted on a wheel with a rim size of 17 x 7 JJ, mounted on a drum tester with a drum diameter of 854 mm under the condition of air pressure of 230 kPa, and rotated (forward or reverse) at a speed of 10 km / m The lateral force generated in the was measured. The obtained results are shown in the column of “conity” as an index that takes the absolute value of the average value of each lateral force and sets the reciprocal of the value of Comparative Example 1 to 100. The larger the conicity index, the smaller the lateral force, which means that conicity is suppressed.

DESCRIPTION OF SYMBOLS 1 Tread part 4 Bead core 5 Bead filler 6 Carcass layer 7 Flipper layer 8 Belt layer 9 Belt cover layer Bi Bead filler height inside when vehicle is mounted Bo Bead filler height outside when vehicle is mounted Fi Flipper layer height inside when vehicle is mounted Fo The height of the outer flipper layer when the vehicle is mounted SH The tire cross-section height

Claims (6)

At least one carcass layer is mounted between a pair of left and right bead portions, and both ends of the carcass layer are folded back from the inside to the outside so as to wrap the bead core and the bead filler embedded in the bead portion, and A flipper layer made of an organic fiber cord is interposed on the inner peripheral side of the folded carcass layer so as to wrap the bead core and bead filler, and a belt layer and a belt cover layer are disposed on the outer peripheral side of the carcass layer in the tread portion. In a pneumatic tire having a configuration and having a specified mounting direction with respect to the vehicle,
The height of the bead filler on the outer side when the vehicle is mounted is made smaller than the height of the bead filler on the inner side when the vehicle is mounted, and the height of the flipper layer on the outer side when the vehicle is mounted is set to the height of the flipper layer on the inner side when the vehicle is mounted. It is larger than the height and its maximum height is 0.7 times or less of the tire cross-section height, and the number of ends of the reinforcing cord constituting the belt cover layer is set to the number of ends on the outside when the vehicle is mounted, A pneumatic tire characterized by being smaller than the number of inner ends.   The difference between the height of the bead filler on the outer side when the vehicle is mounted and the height of the bead filler on the inner side when the vehicle is mounted is in the range of 10 to 50% of the height of the cross section of the tire. The difference in the height of the inner flipper layer is in the range of 20 to 40% of the tire cross-sectional height, and the number of ends of the reinforcing cord of the outer belt cover layer when the vehicle is mounted is the number of inner ends when the vehicle is mounted. The pneumatic tire according to claim 1, wherein the pneumatic tire is 10 to 30% less.   The pneumatic tire according to claim 1 or 2, wherein the reinforcing cord constituting the belt cover layer is a composite fiber cord made of at least two kinds of organic fibers.   The pneumatic tire according to claim 1, 2 or 3, wherein the organic fiber cord constituting the flipper layer is made of non-thermoplastic organic fiber. Characterized in that the ratio _{(E '100 / E' 20} ) of storage modulus at 100 ° C. of the bead filler (E _'100) and the storage modulus at ₂₀ ℃ (E' 20) is 0.5 or more The pneumatic tire according to any one of claims 1 to 4.   The pneumatic tire according to any one of claims 1 to 5, wherein a folding height of the carcass layer is in a range of 0.2 to 0.4 times a tire cross-sectional height.

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